1. Field of the Invention
The present invention is directed to a throttle control system of a secondary engine in a multi-combination vehicle where there are at least two engines, each engine being controlled by a separate throttle control. Typically the multi-combination vehicle includes a truck and a power trailer. A standard pedal throttle provides the throttle control for the truck engine whilst the throttle for the power trailer engine is provided by a separate throttle control, typically a hand throttle. The present invention is particularly useful in the case where the transmission systems of the truck and the power trailer may not be matched, such as the case where the truck transmission is a manual one and the power trailer transmission an automatic one. It is to be understood that the above invention is not limited to a multi-combination vehicle, it may also equally well apply to any vehicle having two or more engines even if it is only one vehicle having two engines.
2. Related Art
Operators of heavy haulage products, such as mines, are constantly searching for ways to reduce the costs associated with hauling their product, in this case ore. One of the most significant costs in operating a mine is transporting the mined material from the ore face to a processing plant. This is exacerbated when the mined payload is of low grade, that is, the desired mineral or metal is only a small percentage by weight and/or volume of the mined ore so that substantial amounts of ore have to be handled to extract a small percentage of desired material. A further problem that occurs is where the ore has to be handled several times.
There are several ways that ore can be transported from the ore face to the processing plant, depending on the type and configuration of the mine.
Underground mines typically have a central lifting or winding shaft to bring the mined ore to the surface. These shafts require a dedicated receival point. To get the ore to that point mines typically have a dedicated rail system that is level and route specific. Underground mine haulage or dump trucks are used to transport the ore from various mining levels both above and below the rail haulage level to the dedicated rail system that then transports the ore to the lifting shaft receival point. The trucks are always a single unit that is either rigid or pivot steered. This type of arrangement has a number of distinct disadvantages.
The dump trucks cause a significant amount of hot air per ton of ore hauled to be exhausted into the mine. Cold ventilation air has to be continually pumped into the mine via ventilation shafts, and one of the major costs in establishing underground mines is the construction and drilling of ventilation shafts. Because of the limitation of currently known dump trucks, the time that they can operate underground is limited, particularly due to excess heat they produce. To reduce the heat, the dump trucks have to move relatively slowly.
A railway system, especially one underground, is relatively expensive to install and operate due to the cost of acquiring the locomotive and installing the fixed railway system and the associated maintenance costs. Furthermore the underground railway system being route-specific is not flexible to changes in route without incurring the expense of installing additional railway tracks. As each new mining area opens, it is necessary to incur the cost of installing new track for the railway system, or to use the dump trucks as described above whose efficiency decreases with the increasing distances they have to travel.
The central lifting or winding shaft is quite expensive, the cost running into tens of millions of dollars and is of a fixed location. As the mine expands the distance from the ore face to the central shaft becomes important in the cost of operating the mine.
In some instances mines have utilized conveyor belts instead of the railway system and/or the lifting shaft. The difficulty with conveyor belts is that once again they are route specific, and are quite expensive to install and maintain. Miners are also concerned that the belts may catch fire and starve the area of oxygen.
In some instances the dump trucks may be used to transport the ore directly above ground. Because of the limitations described above, especially low speed and the heat they produce, and with the inclination within underground mines generally being constant, the depth of a mine that can be realistically accessed by these dump trucks is therefore limited, typically to a depth of hundreds of metres.
When the ore has been transported to the surface, or in the case of an above ground mine, it is then necessary to transport the ore to a central processing plant.
One of the ways that this may be accomplished is by using conventional off-highway dump trucks than can either be a single rigid, pivot steer unit or an articulated vehicle consisting of a very short wheelbase earthmoving type of tractor unit coupled to a single hauled or carrying unit and virtually job specific. These units are designed to be a link in the chain of the actual mining, digging or producing the product. Their main function is to move product from the ore face to a receival point through the shortest possible distance, and they are not route-specific. The shorter the route the more economical they are. The ton of ore transported per distance costs increase dramatically over longer routes. They are therefore not suitable for hauling ore great distances, thereby limiting the distance that ore can be transported at a reasonable cost. As such, these trucks are not suitable when there may be satellite mines, that is, mines that are some distance away from the processing plant. In particular, these trucks have never been designed to be a transportation system for various reasons including the following:                (a) Their axle loadings are extreme and require appropriate roading and bridging. Wheeled or articulated dump trucks with large tires carry a significant loading per axle, up to 33 tons per axle.        (b) These types of trucks are designed for hauling loads over relatively short distances and rough terrain, have relatively large tires for relatively slow speed operation and are relatively expensive to operate and maintain due to fuel and tire costs.        (c) They produce too much heat in both their drive trains and tires. Furthermore they have poor power-to-weight ratios and low operating efficiencies.        (d) Their mass requires a large vehicle cross-section both in height and width.        (e) Their discharge methods are either: direct end-tip (non-captive) where the centre of gravity is always raised, or bottom-dump in the single articulated hauling vehicle that keeps the center of gravity down but is discharge-captive.        
An alternate way of transporting the ore to a central processing plant includes conventional transportation systems such as conveyor belts systems and rail systems, both routes being captive. Problems with these systems have been discussed above.
Another way of transporting the ore is by using highway-type road vehicle combinations or multi-combination vehicles. These vehicles are limited by their horsepower, tractive or braking efforts or capacities, manufacturers' ratings of various componentry, directional stability behaviour, swept path characteristics, gradability and startability.
As a result, currently known systems for the extraction of ore from mines set limits on the commercial usefulness of mines simply due to the cost of transporting the ore.
As discussed above, multi-combination vehicles such as over-the-road vehicles are known. They include a truck coupled to a plurality of trailers and converter dollies. Until recently these vehicles have included a single power source, generally a diesel engine, with the vehicles being limited to a payload of some 170 tonnes, and a gradient not exceeding 5%. These multicombination vehicles, commonly referred to as “road-trains”, have been in use for some time, particularly in Australia, for the purpose of hauling mined products, or the commodities of other industries, over aboveground roadways. Conventional above-ground road-trains are typically designed for use at relatively high speed and on relatively flat ground. They are limited by their horse power, tractive or braking efforts and their capacities that are defined by manufacturers ratings, directional stability behaviour, swept path characteristics, gradability and startability. Accordingly they have limited uses for operation in mines.
The location of the mechanical couplings between each adjacent pair of vehicles in a multi-combination vehicle as described above is positioned to maintain the side-to-side sway, or yaw, of the last vehicle within acceptable limits for above-ground, over-the-road applications. The location is not compatible for operation within an underground mine due to the relatively low operating speeds as well as the relatively narrow tunnels and small radius bends found in underground mines.
Specially configured multi-combination vehicles have been developed recently which have a significantly reduced swept path width as compared to conventional aboveground road-trains. This enables these vehicles to be used to transport various payloads such as mined ores, over the roadways existing in an underground mine. U.S. Pat. No. 6,062,801 issued on May 16, 2000 and U.S. Pat. No. 6,361,269 issued on Mar. 26, 2002, each expressly incorporated by reference herein in its entirety, describe these specially configured multi-combination vehicles which may be used in underground mines. The vehicles can operate in a tunnel system with restricted height, width, swept paths and directional path and can comply with a predetermined behaviour pattern obviating the need for the rail or conveyor system.
Even after the advent of the foregoing specially configured multi-combination vehicles, various operational problems remained to be solved with regard to the transport of mined ores in both underground and above-ground applications. For instance, due to the heavy loads of the road-train combination, the traction provided by the powered wheels of a road-train, usually provided to two rear axles, was insufficient to satisfactorily negotiate the gradients associated with the declines providing ingress and egress to and from some underground mines. Alternatively, these declines into underground mines would have to be constructed at a much gentler slope leading to excessively long tunnels. In addition, the relatively low speed of the road trains underground due to the size of the tunnels and safety considerations results in road-trains travelling underground for a significant length of time, even up to an hour in some cases. This places strain on the road-train cooling system, which is typically designed for aboveground road-trains travelling at significant speeds, generally around 80 km/h. The engines are prone to overheating.
Also, before the introduction of multi-combinational vehicles incorporating a power trailer (i.e., one having a source of motive power), which are subsequently discussed in detail, multi-combination vehicles for dedicated road haulage such as mineral concentrate haulage operated at a 170 ton payload, as noted previously. However, there is a practical limit to the payload of the multi-combination vehicle with a single truck. Since the cost of haulage is determined mainly on weight, if one can increase the total haulage that can be moved by a single vehicle that does not require additional operators, the cost benefit is substantial. This is especially so if ore can be hauled directly from within a mine to a processing plant without needing to be reloaded onto another transport system.
In order to further improve multi-combination vehicles and provide even greater advantages to the operators using these vehicles, multi-combination vehicles have been developed which utilise a truck and an additional motive power source advantageously located within the chassis of a trailer and which include a unique cooling system that enables operation of the multi-combination vehicle at low speeds, on steeper gradients and with a greater payload than previously known. International Patent Application No. PCT/AU01/01154, expressly incorporated by reference herein in its entirety, discloses a multi-combinational vehicle including a power trailer having an engine that overcomes the foregoing problems of traction and cooling of such multi-combination vehicles. International Patent Application No. PCT/AU01/01568, also expressly incorporated by reference herein in its entirety, discloses various features that may be incorporated in the drive trains of multi-combination vehicles of this type. These multi-combination vehicles, which have the ability to traverse different mining levels, have removed the need for conventional dump truck haulage from the ore face to the rail head, and also have enabled the vehicle to haul ore directly from the ore face from any underground level via an access tunnel directly to a processing plant, thereby eliminating the need for the lifting shaft. Furthermore, these types of multi-combination vehicles coupled with specifically configured power trailers, typically B-double trailers, can be used above ground to transport ore directly to a processing plant eliminating the need for other dump trucks, increasing the total payload from some 170 tons to 270 tons whilst staying within the manufacturer's rating and at the same time increasing the general behaviour pattern, thereby creating a safer multi-combination vehicle.
Use of a multi-combination vehicle using a truck and a power trailer provides a further significant advantage over conventional single-engine dump trucks, and over multi-combination vehicles having only a truck. Even if one of the engines and/or transmissions fails there is the potential to use the second engine to at least move the multi-combination vehicle out of the way or even bring it to the surface for analysis and repair. As known in the art, in the event of engine and/or transmission failure it is more than a simple exercise to retrieve a single-engine dump truck from the depths of an underground mine that is then blocking the underground road from use by other trucks. A similar problem may exist with multi-combination vehicles powered only by a single truck, or in some instances a single prime mover.
International Patent Applications PCT/AU02/00667 and PCT/AU02/00668, disclose various features in a multi-combination vehicle of the type having two engines that enable at least one engine or transmission to operate and provide propulsion to the vehicle even if the other were to fail. These two applications discuss an arrangement whereby control of both of the engines is provided by a central control system, such as the throttle control pedal used by the driver. Accordingly they rely on the two engines and transmissions systems being generally of the same capacity and type, such as having identical automatic transmissions.
However, there may be instances where it may be desirable to provide a multi-combination vehicle combining a power trailer with an automatic transmission system to an existing truck running a manual transmission system. This is especially so if one considers that the majority of current trucks that are used in road-trains are ones utilising a manual transmission system.
One of the difficulties in such an arrangement is that the power trailer engine needs to be controlled by a separate control system rather than the truck throttle pedal. Coupling a power trailer running an automatic transmission to the existing truck throttle would not work. Every time the driver changed up a gear as the truck is accelerating they would remove throttle from the truck and trailer With no fuel received by the trailer engine the automatic transmission would gear down whilst the truck transmission would be geared up. When the truck higher gear is then engaged, the trailer transmission is in the completely wrong gear causing undue stress on the trailer engine and the transmission.
For that reason it is necessary to provide for a separate trailer engine control that is operable by the driver independently of the truck engine.
However, having an independent control for the trailer engine is in itself a problem if for some reason the truck engine powers down very quickly or the driver applies heavy or emergency braking. In an emergency the normal procedure is for the driver to apply the foot brake. However, the power trailer engine continues to operate according to its throttle position independent of the application of the foot brake by the driver. This causes the power trailer engine to keep applying propulsion even where the driver has initiated emergency braking.
The inventor is unaware of any multicombination vehicle having a manual transmission truck and a powered trailer, whether it is for above ground or underground use of the type described above, where the throttle control for each engine is independent and where the power trailer engine throttle is disengaged or bypassed when the driver applies braking, in particular emergency braking.
In view of the foregoing disadvantages and limitations associated with known load-carrying vehicles, a commercial need exists for an improved load-carrying vehicle combination for use both aboveground and in underground mines that overcomes at least some of the abovementioned problems or provides the public with a useful alternative.